3) How Changing F-Stops Affects Your Photos
Every time you move from one f-stop up or down to the next, you are either doubling or halving the amount of light going through the aperture. As the f-stop number goes up, the amount of light going through the aperture decreases. It can be confusing, because it seems like a larger f-stop would indicate a larger opening in the lens. But that isn’t the case.
The f-stop scale has fooled many into thinking that the bigger the f-stop number gets, the bigger the opening in the aperture is. It’s actually the other way around.
Because of the way the aperture size is calculated (much too complicated to explain here), as the f-number gets larger, it actually means that LESS light is going through the aperture and that the aperture is getting SMALLER.
So, an aperture set at f-4 is a larger opening in the lens than an f-stop of f-22.
When you open up the aperture one stop, you are letting twice as much light through, which makes the picture brighter. If you close the aperture down one f-stop, you’ll be decreasing the amount the amount of light going through in half, which makes the picture darker.
Here’s a handy chart to help you remember common f-stop settings.
If you get mixed up, just remember to look at the chart above to help you out. You can even print it out and carry it around with you for a while until you get used to this idea.